WESTCODE An IXYS Company
IGBT Gate Driver Type C0044BG400
Optical Feedback Signal, Error Management and Soft Turn OFF Timing
The optical feedback signal is a mix of a “real IGBT ON-echo” signal, power good condition and IGBT short circuit
detection. It uses a transmitter (TX) type “versatile Link family” HFBR-1521 (5M-Baud).
With all secondary side supply voltages in “power good” status and no “ON command” at RX present, the feedback
signal is illuminated with typical 35 mA.
If an ON command at RX occurs for longer than the short pulse suppression time the IGBT gate will be switched to
ON status (after driver propagation delay ON time). As soon as the IGBT reacts correctly and it’s VCE meets the trip
level of 25V, the feedback signal will switch off TX light and act as a “real IGBT echo” (within propagation delay of the
internal VCE0 signal).
If a PWM OFF command (longer than short pulse suppression OFF time) occurs at a VCE < 25 V condition the IGBT
gate is switched off with both (normal and soft turn OFF) amplifier paths regulated to -15 V. This is considered a
normal/ fast turn OFF operation.
If VCE never reaches the trip level or VCE increases during an ON command above the trip level, the feedback signal
reports a VCE-desat error by switching ON the TX light while a PWM ON command is present at RX.
Please note that this is a way for the user to detect a VCE-desat error monitored by the driver.
In this version of the driver family the driver does NOT turn OFF automatically. The PWM OFF command has
to be generated by the user and the user has to take care of adequate guidelines to reach a tolerable OFF time
delay. (Typical waiting time several µsec, depending on IGBT type).
Any OFF user command at VCE > 25V will be executed by the soft turn OFF path only.
After a soft turn OFF time of typically 30 µsec the IGBT should have switched successfully into a safe OFF status.
After this soft turn OFF time the normal/ fast turn OFF path is enabled again, to provide low impedance OFF status at
the gate like in nominal current turn OFF condition.
RX signal (PWM)
VCE > 25V
TX signal (feedback)
00 I I 00 I I
0000 I I I I
0000 I I 0 I
Table 1: Logic State of Feedback TX/ RX Signal (I = light ON)
Turn OFF Timing with and without Vce Trip
Figure 5: Switch OFF at normal operation (no VCE-desat
Figure 6: Switch OFF at VCE-desat trip
Ch1: Internal „Soft-OFF“enable command
Ch2: Collector-emitter voltage
Ch3: Internal „Fast-OFF“ command
(= low impedance OFF) state
Ch4: RX PWM light command
Please note: Soft turn OFF time was set to 81 µsec here!
Under Voltage Error Management
This driver monitors all supply voltages generated on the secondary side with defined power good levels and a large
hysteresis. Power good condition is given when desired voltage levels are nearly reached for the first time. Once
power good is generated, it accepts a fairly low supply condition until the power good signal fails. Once power fail is
detected the gate output is forced into IGBT OFF state and feedback signal TX will turn OFF normal/ fast.
Provisional Data Sheet Type C0044BG400 Issue A1
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